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Post by pxguru on Oct 28, 2014 17:37:41 GMT
Wow, you have been busy Just need to add a box in your little calculator to offset the static deck height ((how much the piston is below from TDC) there is always some thing!) It won't be long now until you realise you havent asked the actual real question yet
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Post by pxguru on Oct 28, 2014 6:57:31 GMT
Not sure the books will help you so much. They are a little more theoretical than practical. That timing calculator on scooterhelp works perfectly. 57mm stroke and 105mm conrod on a standard PX125/150. Transfer port timing is normally stated in total duration time. The time the ports are open within the 360 degree period. The ports are obviously open the same amount of degrees either side of BDC.
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Post by pxguru on Oct 27, 2014 5:38:36 GMT
The starting point for me with setting the barrel height correctly, is as above, top of piston/rings with bottom of exhaust port... Anyless than that, the pistons rings wont stay as cool, exhaust port is open for shorter period too, less time for hot gases to escape, heat build up, blah! Blah,blah! The further the piston travels down past the bottom of the exhaust port, the more cooling the rings will recieve. It will also giving you longer exhaust port timing, which can be used to your advantage too! But for me id prefer to see that piston get back up to TDC again as fast as possible, not hang around below the exhaust port... Thats a good base point to start at anyway, for any 2stroke cylinder. From there you can experiment! Remember when you raise the cylinder and use the same head you will loose a little compression, as the volume of the combustion chamber increases. For example, (from memory) on my pinasco 225cc, for every 0.38mm i raise my cylinder, i would gain 1cc volume in the head, and obviously also increase my squish gap, which would also lower my compression. I think we're all singing from the same songsheet, just maybe different verses! For me setting of the barrel height is not directly about the exhaust port. Keeping the rings covered when the exhaust is fully open is totally true and necessary but not the focus of the set up. When setting up the height of a barrel it is the height of the top of the main transfer ports which is the highest priority. The exact amount of degrees set here for the decided purpose of the engine is fundamental for the entire engine set up. The closer the degrees are set to optimum without going over the more power there will be.
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Post by pxguru on Oct 26, 2014 11:28:31 GMT
Oh look what I started Just to get one thing straight, all I will suggest on here are things that will do no damage and can be reversed. And changes that will generally make your scooter faster will usually be less economical. Standard looking fast scooters are currently my thing. One thing about kits is they are made to fit any engine. As every engine is different in terms of tolerances a kit will rarely ever be perfectly set straight out the box. The one easy thing anyone can do with DR kits is set the barrel height, this is really important if your aim is to get the most power out of it. DR tend to be always under, or way under. For a standard DR kit the squish clearance is not as important as the barrel height, anywhere between 1 and 3 mm squish on a standard DR is fine.
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Post by pxguru on Oct 26, 2014 4:03:04 GMT
Or you could put on about 5 or 6 standard ones (all trimmed as Nik said) to make 1mm thick and then at least it would go properly
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Post by pxguru on Oct 25, 2014 8:13:15 GMT
I wouldn't recommend using 603 on anything apart from the clutch seal. Just too difficult to get bearings out stuck in with 603. I never use anything on bearings and not had an issue.
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Post by pxguru on Oct 22, 2014 17:18:10 GMT
If its any help at all, I only ever fit the same, brown metal seals, in any motor. Once they are bonded (loctite 603)and dot punched they are not going anywhere. No matter how high it revs or how hot it gets. Taping the cases and screwing them in is a little extreme but I can see the point The seal on the rotary valve pad is really not so important. As long as there are no side gaps and it takes a few seconds to empty the well of petrol its fine.
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Post by pxguru on Oct 20, 2014 12:39:57 GMT
If there is hissing from the clutch breather when the crankcase is under pressure then there is a problem. I normally test to 10 psi for 10 minutes. If it can't hold this pressure then it will lose power at high rpm. Sorry but no choice except split it. If you have just fitted a new metal seal it might be leaking through the outer edge. Need to always bond them in and dot punch. Testing the gearbox by pressurizing it is risky in an engine you will not be splitting. The clutch side seal has a large surface area and pressure from the clutch side can blow it out of its seat. If you are going to do this then 1 psi max. Years ago I used to really worry about rotary Valve pad wear but as long as you can tip petrol in the inlet and it stays filled for a few seconds its plenty good enough. A new engine will hold petrol for minutes but this is just showing off
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Post by pxguru on Oct 18, 2014 18:08:40 GMT
Hissing from the gearbox breather is not good. Might still appear to run fine but would be a few horses short Will be interested to know what is leaking...
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Post by pxguru on Oct 13, 2014 18:27:54 GMT
i was reading something a while back about tuning a standard px125,,raising the cylinder with a base plate,skimming the head and porting the monkeys outa it,,supposedly you can make it pretty snappy without a kit,not much top speed though,,then seeing twin carbs and 5 speeds i wondered what else was done,,what did you use for porting and what was buying parts like before the internet? As H said as well, each engine has a sweet spot which can be found by raising the barrel. None are ever right from the factory due to the precision Italian tolerances. Even if your engine is totally standard setting the barrel height to where it is supposed to be (like blue printing) could make a nice power increase.
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Post by pxguru on Oct 8, 2014 7:43:45 GMT
I can't understand why the motor needs to be fully re-built. It only heat seized. The piston was chipped when it was chucked against the wall. That Malossi barrel still looks usable with a new piston. Malossi barrels give the most power with an expansion type exhaust like a JL-RZ. Otherwise a SIP Road 2
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Post by pxguru on Oct 5, 2014 7:10:23 GMT
I even verified it was jetted properly for a stock motor. Did you actually change the jet to a standard 118? Or was that already in there? The seize marks are the unfortunately not unusual "running weak over heat" I hope the broken piston skirt was done getting it out of the barrel or chucking it across the garage. Malossi don't make oversize pistons, so you can forget that idea. The ally barrel liner is very hard, so if as Nik says you can't catch a fingernail in any of the score marks (above the exhaust port level is the most important) then you have been very lucky and can re use the barrel with a new Malossi piston. I would familiarise yourself with the "Sime66 six biscuit scale" when you get it running again vespa.proboards.com/thread/4347/spark-plug-question
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Post by pxguru on Sept 30, 2014 8:28:01 GMT
Could possibly be a damaged clutch basket. Will need to take the clutch out to inspect it. I wouldn't ride it too far from home until I knew what this was
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Post by pxguru on Sept 24, 2014 18:18:42 GMT
I'm thinking you're a bit to easily put off to get into tuning Matching and filling transfers is in my fine tuning for speed catagory, as is squish bands and custom heads and everything else. Your base engine is good as it is. I think for what you have mentioned, just a DR barrel rebored with a new piston, ported to perfection for torque. And some kind of expansion exhaust and thats it. Loads more torque and +5mph. easy.
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Post by pxguru on Sept 24, 2014 4:10:11 GMT
Sime66, What I was basically meaning, was instead of spending loads on a replacement whole or half engine, have a think about what you are really trying to achieve. As with all tuning projects first thing is to work out what you need from it in terms of performance, economy, reliability, max rpm, power band, torque etc. Then balance that against the budget. How you fit the all tuning parts together is often as important, as buying the right parts in the first place. I think for yours you just want a bit more speed with no less reliability. All you really need is a barrel, piston and a decent expansion. No need to modify anything else in the engine from what you have recently done. And you already have a 24/24 on it. When I started out tuning my first PX (31 years ago!) I made a whole new engine and left the standard one in a cupboard for ages, then eventually sold it
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Post by pxguru on Sept 23, 2014 16:53:15 GMT
Sime66, I doubt you are after a full blown race scooter. The majority of any actual performance increase is just in the brarrel. If you got yourself an old/scored up DR180 barrel and a Dremel, learn some tuning, quick rebore and your Dale Winton will be doing over 70mph
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Post by pxguru on Sept 23, 2014 7:00:29 GMT
I don't like the look of any of them These show the kind of jetting that can cause a sieze up when the weather changes and why we do plug chops. I would up the main jet at least 5 (125 to 130?) and fit a brand new B8ES, as its the one that looks like the right heat rating to me. Once jetted better this could change a little. For anyone taking plug pictures please try to get the bottom of the insulator cone in view.
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Post by pxguru on Sept 23, 2014 6:48:50 GMT
I'm still not convinced it isn't the clutch side oil seal. If seal has not fully let go then it can still fit what you are seeing.
If not that the then my money is on the stator pick up.
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Post by pxguru on Sept 22, 2014 4:59:34 GMT
Honing Nikasil is a bit of a skilled job A quick go over with some scotchbrite is far safer. What is your timing at now? I have visions of it being set fully clockwise!
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Post by pxguru on Sept 21, 2014 4:54:56 GMT
fpb, If you rev counter is correct then thats some big clutch slip you have Did it stink when you took it out? If its an old 3 plate then its no surprise. I adjust to tick over at 900 with clutch pulled in and lights and indicators on. Just for normal road use the gearing should be set so that it maxes out at about 500 rpm less in 4th than it can rev to in 3rd. I am certain you will need to fit at least a 21 tooth.
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Post by pxguru on Sept 21, 2014 4:33:26 GMT
This can of worms diagram I believe to be true and is just relevent to 2 strokes. If you can see the three bands on the insulator cone and a digestive colour on the tip then the jetting is close enough. On a 125/150/180 head the plug goes in at a steep angle and one side is close to the piston and the other isnt. this makes the plug reading difficult. All that shiny black gunk inside your plug ideally should be more matt finish and bourbon coloured. When I said compression I really meant squish clearance. The squish band forces the mixture to mix better and burn more completely. Whats your timing set to? It's nothing to worry yourself about. Just leave it like this and it should go fine for many years yet. Burning better will save fuel though
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Post by pxguru on Sept 20, 2014 10:14:27 GMT
Sime66, Can't quite decide if your plug is too much 2 stroke or not enough compression. Jetting is close enough for being cautious. As is the plug heat rating. You're not running autolube are you? I think you are putting too much oil in. If you use a decent brand then 50:1 two stroke is ample up to 10,000 rpm. no need to add extra, it just messes up the performance
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Post by pxguru on Sept 18, 2014 9:51:50 GMT
With things like this, when everything else has been checked it is always worth checking that it isnt the clutch side oil seal. How is the gearbox oil and level?
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Post by pxguru on Sept 17, 2014 18:14:17 GMT
Nothing wrong with std gearing for a Pinasco, so you just have a few horses loose somewhere. A little leak won't lose this much. What did you set the timing to when you put it back together? The Pinasco kit can run the standard 23 degrees on the 'A' mark without any issue if the carb is set up well. If you are a bit nervous with your jetting, then just adjust back the width of the timing mark (2mm).
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Post by pxguru on Sept 17, 2014 6:18:12 GMT
Not so cheap but I got one of these CDIs for my Polossi last month www.kheper-scooter.comWas a bit tricky to get fitted under the panel without touching the back of the indicator but well impressed with the performance and fiddle ability on the laptop. Extra torque to counter my lard and 2mph quicker on the first program I ran A programable CDI gets totally over the problem of needing advanced timing at low rpm and retarded timing at high rpm.
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Post by pxguru on Sept 17, 2014 4:37:58 GMT
Impressive post but can't resist going over a few points.
6) A lot more to it than that! A long stroke crank fitted in a barrel ported (or made for) for a short stroke crank will make the scooter more sporty and rev higher. Trying not to be scientific at all; a piston does not travel at a constant speed, as it needs to turn around and come back up, while its down the bottom going further the ports remain open a little longer letting in more mixture. More mixture being compressed, more bang, more revs. You can vary the amount of max revs with base gasket thicknesses but even the thinnest will rev higher than the short stroke crank would have in the same barrel. A long stroke crank in a barrel made for a long stroke crank will make an excellent tourer.
7) The PX has excellent cooling and actually doesnt get hot enough in the UK heat. There are never temperature issues if the carb is set up right at all throttle positions.
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Post by pxguru on Sept 16, 2014 17:17:16 GMT
If it revs as high in 4th as in 3rd it needs up gearing. If you can get 4th gear within 500rpm of the max rpm in 3rd then the gearing is about right. What are your max revs in 3rd?
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Post by pxguru on Sept 16, 2014 16:56:59 GMT
Sime66, The biscuit scale is just perfect Mines a bit digestive on the tip and oreo ring at the base of the cone, just the way I like it. Taken in the services after about 20 mins on the motorway.
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Post by pxguru on Sept 15, 2014 7:40:24 GMT
How did the pilot jet work out? What size you end up with?
Can you remind me what gearing you have, or is it all standard 200?
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Post by pxguru on Sept 15, 2014 7:36:52 GMT
Lovely looking plug
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